1. Field of the Invention
The present invention relates to an apparatus for determining the degradation of oil circulated in and supplied to various parts of an engine. Especially, the present invention relates to an oil-degradation determination apparatus for determining the degradation of oil circulated in and supplied to the engine, on the basis of measured data on an electric pump used for circulating and supplying the oil, without using a sensor or the like to directly detect the viscosity or other parameters of the oil.
2. Description of the Related Art
Engine oil that is circulated and supplied to the cylinder-wall surfaces and the bearings of an engine mounted, for example, on an automobile or a motorcycle is gradually degraded as the vehicle travels. Accordingly, it has been conventionally recommended to change the oil to new one on the basis of either a travel distance or the period of its service.
Specifically, a common way of determining when to change the engine oil is to record a travel distance and to change the oil once the vehicle has traveled a predetermined distance on the basis of the recorded travel distance (a travel-distance integration method). Another way thereof is to always detect the condition of the engine oil by use of a sensor, and to change the oil when the degradation of the oil is observed by the sensor (detection-by-sensor method). More specifically, as Patent Document JP-A-3-26855 and Patent Document JP-T-2003-524169 describe, the condition of the engine oil is determined on the basis of physical properties of the oil, such as the viscosity and the non-permittivity of the oil, and the oil is changed when the oil is degraded.